1. Field of the Invention
The present invention relates to a liquid crystal display apparatus and a fabrication method thereof, in particular, to a liquid crystal display apparatus having a controlled display pixel light transmittance and a fabrication method thereof.
2. Description of the Related Art
Liquid crystal display apparatuses have been widely used because of their characteristics such as thin size, light weight, and low power consumption. For example, liquid crystal display apparatuses have been used in various fields including computers, car navigation systems; and TV display systems.
In recent years, liquid crystal display apparatuses that have large display screen and/or high resolution have been required. Accordingly, liquid crystal display apparatuses having large screens at least of 14 inches in diagonal distance and/or fine display pixel pitches of 100 .mu.m or less have been studied and developed.
Those liquid crystal display apparatuses having such large screens and/or highly precise display screens are likely to increase the occurrences of defective pixels that take place in the display screen.
Although the occurrences of defective pixels may be reduced to some extent by properly designing the liquid crystal display apparatuses or improving the fabrication processes thereof, the problem of the defective pixels have not been completely solved. The defective pixels are those having different voltage (V)-light transmittance characteristics than normal pixels.
To mute the defective pixels, for example, an attempt for designing a liquid crystal display apparatus with redundancy has been made. In this attempt, a repair function is provided so as to fix the defective pixels. However, such a repair function cannot deal with various defects. Thus, satisfactory avoidance of defective pixel occurrences cannot be achieved.
In the case of defective pixels the display quality of the liquid crystal display apparatuses is remarkably deteriorated, and there are luminance point defects that take place by various causes.
Hereinafter, in a so-called normally white mode liquid crystal display apparatus where the light transmittance is maximum when the potential between the pixel electrodes is lower than a predetermined threshold value or less of the liquid crystal layer, the luminance point defects represent defective pixels where light transmittance does not decrease corresponding to the electrode potential On the other hand, in a so-called normally black mode liquid crystal display apparatus where the light transmittance is minimum when the electrode potential is the predetermined threshold value or less, the luminance point defects represent defective pixels where the light transmittance does not decrease when the potential between the electrodes is equal to or less than the threshold value of the liquid crystal layer.
Even if one luminance point defect is present on the display screen, since the value of the liquid crystal display is critically deteriorated, the countermeasures against the luminance point defects should be quickly taken.
As one of such countermeasures against defective pixels, such as luminance point defects, a method as disclosed in Japanese Patent Laid-Open Publication No. 60-243635. In this method, laser light is radiated to a defective pixel so that an orientation film and a pixel electrode are burnt and thereby the alignment characteristic of the liquid crystal material of the liquid crystal layer is lost. This method is used to mute abnormal light transmittance observed as various defective pixels.
However, the effect for removing the luminance point defects in this method is less than expected.